This invention relates generally to spectrophotometers, and more specifically relates to colorimeters of the type used for determining the presence and concentrations of chemical species in a liquid or gaseous sample containing such unknowns.
Highly sophisticated and complex spectrophotometers are widely used in the course of analyzing chemical systems. In a typical such device e.g. a wide-band source of light (e.g. in the visible or U-V spectrum) is processed through a monochromator, which may include a dispersion element such as a prism or grating, and an attendant wavelength drive mechanism for rotating the dispersion element to enable a series of wavelength outputs at relatively discrete frequencies. A sample subjected to analysis in such an instrument is traversed with a beam of light at successively varying wavelengths, and the resulting attenuation of the light beam is converted to a read-out indicative of the absorption or transmission characteristics of the sample. In many instruments of this type a so-called dual-beam mode of operation is employed -- which while adding to the accuracy of the instrument, adds further complexity to the optical and electronic systems of the instrument.
Over the course of years, numerous colorimeters have been proposed, which are in essence highly simplified versions of the relatively sophisticated device described above. Interest in connection with these devices has centered, among other things, upon providing an instrument of relatively limited size and complexity, which might nevertheless provide accurate information with respect to at least certain absorption characteristics of a sample. Numerous of these prior art colorimeters have sought to incorporate or use a probe element, or similar means, which might be directly insertable into a liquid or gas sample, thereby eliminating the need for a cuvette assembly -- together with the attendant problems of such assemblies.
Notwithstanding however, the considerable interest evidenced in providing colorimeters of the foregoing type, such instruments as have in the past been proposed, have not met with high commercial acceptance, and a need continues to exist for such an instrument.
In accordance with the foregoing, it may be regarded as an object of the present invention, to provide a highly accurate and dependable colorimeter, which is so compact as to be hand-holdable, and which includes a probe portion directly insertable into a liquid or gaseous sample.
It is a further object of the invention, to provide a compact and accurate colorimeter, which enables measurements of colorimetric properties at discrete frequencies, and without the necessity for conventional monochromaters, filters, or for complex mechanical or electronic light choppers.
It is yet a further object of the invention, to provide a hand-held colorimeter, which while eliminating the complex monochromators and electronic circuitry normally utilized in sophisticated spectrophotometers, enables a direct comparison between input and transmitted light levels, to thereby yield highly accurate results.